Why do wind turbines always have three blades?

8:44 PM 1 Comment

If you have seen a wind farm, you have noticed that wind turbines have 3 blades. Why not 1 blade, 2 blades, 4 blades or 5 blades ? Because the aim is when the power is produced not to capture more wind. The aim is capturing wind with greatest efficiency. And as a result it is found that 3 blades is the most efficient and less troublesome way.

 Wind turbine with one blade

It is not common but when you see a wind turbine with one blade, you shouldn't surprise. It looks like a little different from the other common wind turbines even the working principle is same. Due to one blade, it is cheaper from the others. On the other hand the aesthetic of the one bladed turbine is a little worse. Whole wind energy sector compromise about 3 blade wind turbines due to aesthetic. If we look more detail, the efficiency of the one bladed turbine is higher, but the loads are also higher due to unbalance rotor. What's more it tends to spin faster. That's why it is much more noisy.

2 bladed offshore wind turbine

As it seen the previous figure, sometimes two bladed wind turbines can also be seen. The same phenomena about aesthetic is valid for two bladed wind turbine also. But this has higher efficiency than the one bladed and 3 bladed wind turbines. When we compare with 3 bladed wind turbines, the only advantage  is one blade is less, that's why it is cheaper. It is cheaper from the rotor side but on the other hand  because of higher loads the maintenance costs and the life of turbine must be considered also. 

3 bladed wind turbine 

Due to aesthetic, efficient loads 3 bladed wind turbines are much more common. When it is compared with the other types of wind turbines, powerful enough and it is less noisy because of tending to spin slower. Noise issue is also must be considered when a wind turbine constructed. Because of these reasons 3 bladed wind turbines are accepted in wind energy sector.

Wind turbine with 5 blade

When the number of the blades are increasing, normally cost of turbine is also increasing. That's why the turbines which have more than 3 blades seen rarely. If we look from the technical side, when we have more than 3 blades, we must make them lighter. When they are lighter, they will tend to spin faster and they will be broken. That's why generally it is not good idea to use more than 3 blades. 

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Maglev Wind Turbine

11:03 AM 175 Comments

The Maglev wind turbine is the one of the type has interesting design. Working principle of the turbine is a little differ from the other ones. Magnetic levitation differs this turbine from the other classical turbines. Why magnetic levitation ? Magnetic levitation is one of the most efficient system for the wind energy.

Maglev wind turbine

As it seen in the picture also, it is a vertical axis wind turbine. Vertically oriented blades of the turbine are rotating above the base of the machine. As a generator, full permanent magnet wind generator is used. Therefore it is not using electricity from the grid to run. The Maglev uses a magnetically levitated low-RPM high-torque power output turbine. As it known, because of the permanent magnets, there is no energy loss through friction. Hence the maintenance costs are automatically dropped when we compare with other classical wind turbines. 

Maglev prototype

Actually Maglev is not new technology. It has same phenomena with high speed trains in Europe and Asia. It is designed to capture winds from any direction. It means this turbine has not yawing issues. That's why we can say the Maglev turbines convert wind energy to electric energy in a extremely sufficient way.

Offshore maglev turbine

 If it is compared with other classical wind turbines, 
Maglev, 

• is producing 50% more power.
• construction is cheaper.
• has no noise.
• can produce with small and high wind speeds.
• Important components are on the ground level.

Vertical axis wind turbine

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Wind Generator

6:17 PM 1 Comment

The wind turbine generator converts mechanical energy to electrical energy.
Wind turbine generators are a bit unusual, compared to other generating units you ordinarily find attached to the electrical grid. One reason is that the generator has to work with a power source (the wind turbine rotor) which supplies very fluctuating mechanical power (torque).
These pages assumes that you are familiar with the basics of electricity, electromagnetism, and in particular alternating current. If any of the expressions volt (V), phase, three phase, frequency, or Hertz (Hz) sound strange to you, you should take a look at the Reference Manual on Electricity and read about alternating current, three phase alternating current, electromagnetism and induction before you proceed with the following pages.

Wind genearator

Generating Voltage (tension)
On large wind turbines (above 100-150 kW) the voltage (tension) generated by the turbine is usually 690 V three-phase alternating current (AC). The current is subsequently sent through a transformer next to the wind turbine (or inside the tower) to raise the voltage to somewhere between 10,000 and 30,000 volts, depending on the standard in the local electrical grid.
Large manufacturers will supply both 50 Hz wind turbine models (for the electrical grids in most of the world) and 60 Hz models (for the electrical grid in America).
Cooling System
Generators need cooling while they work. On most turbines this is accomplished by encapsulating the generator in a duct, using a large fan for air cooling, but a few manufacturers use water cooled generators. Water cooled generators may be built more compactly, which also gives some electrical efficiency advantages, but they require a radiator in the nacelle to get rid of the heat from the liquid cooling system.
Starting and Stopping the Generator
If you connected (or disconnected) a large wind turbine generator to the grid by flicking an ordinary switch, you would be quite likely to damage both the generator, the gearbox and the current in the grid in the neighbourhood.
You will learn how turbine designers deal with this challenge in the page on Power Quality Issues , later.

Small wind generator

Design Choices in Generators and Grid Connection
Wind turbines may be designed with either synchronous or asynchronous generators, and with various forms of direct or indirect grid connection of the generator.
Direct grid connection mean that the generator is connected directly to the (usually 3-phase) alternating current grid.
Indirect grid connection means that the current from the turbine passes through a series of electric devices which adjust the current to match that of the grid. With an asynchronous generator this occurs automatically.

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Wind Turbine Costs

7:21 PM No Comments

Wind turbines, including the costs associated with blades, towers, transportation and installation, constitute the largest cost component of a wind farm, typically accounting for around 75% of the capital cost. Wind turbines tend to be type-certified for clearly defined external conditions. This certification is Source: Wind Directions, January/February 2007 requested by investors and insurance companies, and states that wind turbines will be secure and fit for their purpose for their intended lifetime of around 20 years for onshore projects and 25 years for offshore. The following illustration shows the main sub-components that make up a  wind turbine, and their share of total wind turbine cost. Note that the figure refers to a large turbine in the commercial market (5 MW as opposed to the 2 to 3 MW machines that are commonly being installed). The relative weight of the sub-components varies depending on the model.

To make the illustration bigger :  Wind turbine costs

Wind turbines are priced in proportion to their swept rotor surface area and generally speaking in proportion to roughly the square root of their hub height. The size of the generator of a wind turbine plays a fairly minor role in the pricing of a wind turbine, even though the rated power of the generator tends to be fairly proportional to the swept rotor area. The reason for this is that for a given rotor geometry and a given tip speed ratio, the annual energy yield from a wind turbine in a given wind climate is largely proportional to the rotor area. In relation to tower heights, the production increases with the hub height roughly in proportion to the square root of the hub height (depending on the roughness of the surrounding terrain). It should be noted that the generator size of a wind turbine is not as important for annual production as the swept rotor area of the turbine. This is because on an optimized wind turbine, the generator will only temporarily be running at rated (peak) power. It is therefore not appropriate to compare wind turbines with other power generation sources purely on the basis of the installed MW of rated generator power. One has to keep in mind that the energy of a wind turbine comes from the swept rotor area of the wind turbine. The swept rotor area is thus in some sense the field from which the energy of the wind is harvested. 

Wind lamp

To read more about economic facts about wind turbines, see : The cost of energy generated by wind

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Sizing Up Wind Energy and Transportation

6:24 PM No Comments

One of the most popular trends in sustainable living is to go small: Live in a small house. Drive a small car. Have a small carbon footprint. So it seems contradictory that by going big—really big—energy equipment can become better for the environment.

But that's the case with wind turbines, according to a new study by the Swiss Federal Institute of Technology in Zurich.

Over the past 30 years, wind turbines have more than quadrupled in size. The blade diameter of today's models can surpass the length of a football field. In tandem with this growth spurt, land-based turbines in Europe became greener, the researchers concluded.

The report, published in the American Chemical Society's journal,Environmental Science & Technology, looked at the energy it took to build, transport, maintain, and dispose of turbines, as well as the electricity the turbines fed into Europe's power grid.

Turbines became more sustainable over time because larger models produce substantially more energy than smaller versions, the researchers said, but it does not take as much additional energy to manufacture bigger turbines. And as more turbines were built, manufacturers became more experienced and technology improved. With each doubling of wind-turbine manufacturing over time, the Swiss researchers found, the global warming potential per kilowatt-hour of electricity dropped 14 percent.

Marloes Caduff, the lead author, said she was surprised by how much the carbon footprint of the turbines declined over time. "I thought we would see a smaller effect," she said.

The industry, for its part, has tackled many of the challenges of larger turbines—for instance, how to move them from one place to another. Even so, companies believe there will be challenges for further growth in turbine size, even as the industry seeks to further improve their efficiency.

Why Bigger is Better

Bigger turbines reach higher above the earth's surface, where stronger winds blow. This allows them to extract more energy than their predecessors, and to work more efficiently.

In the 1980s, a typical wind turbine was rated with a capacity of about 50 kilowatts of electricity. Today, a large land-based turbine has a capacity of 3,000 kilowatts (3 megawatts). There are developers working on wind turbines as large as 10 MW for offshore installations. But on land, the most common turbines are from  1.5 MW to 2 MW. A 1-MW turbine can power 350 U.S. households for a year, according to Wind Energy America.

Using higher-capacity models reduces the number of turbines needed for a wind farm, says Fort Felker, director of the wind technology center at the U.S. Department of Energy's National Renewable Energy Laboratory in Golden, Colorado. For example, at today's capacities, 500 super-sized turbines could be installed instead of 1,000 smaller ones. By generating more energy with fewer machines, giant turbines can help reduce the price of wind power.

"The larger-size wind turbines result in dramatic reductions in the cost of [wind] energy," Felker said. "The cost has been reduced by a factor of ten or so, from unaffordable levels to where it is right now, able to compete with conventional power sources."

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Increasing the Efficiency of the Wind Turbine

10:37 PM 1 Comment

Blades are important components that need to be matched with the wind speed environment in order to maximize the efficiency of a turbine. At low wind speed, more blades will be better and the blades should be long and wide. The blade pitch should be large. At high wind speed, the blades should be short and thin. The blade pitch should be small then. The number of blades is also an important parameter of a wind turbine. You may install 1 to 6 blades on the WindLab to see the effects, even if the blades are not balanced symmetrically.

However, it is difficult to test these parameters on a real wind turbine. Even if you can change the blade parameters on a real wind turbine, you cannot command the speed of the natural wind for you to test the result.

WindLab allows you to evaluate these parameters easily. It comes with a set of 3 blades and 1 vane, which are cut from flexible plastic (Polypropylene) sheets, for you to start with. The design concept is to let you design your own blades and vanes with easily available plastic or paper card sheets. Scissors and Punch are the standard stationery needed to work with your knowledge and imagination to create your own blades and vanes. You can modify the number, size and shape of the blades to see how the output is affected at different wind speed. You may also modify the size, shape and color of the vanes to make fun with it.

WindPitch allows the evaluation of Blade pitch and profiled blades. Mechanism for installing sheet blades is also included so that blade sizes and shapes can also be evaluated. However, WindPitch does not have an internal Gold Capacitor to store the generated electricity internally.

WindCharge can be used as a basic turbine for generating electricity for some applications. The blade pitch on the WindCharge Plus is optimized to an angle that maximizes the output of the turbine.

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How Much Power Can We Extract from the Wind

6:44 PM 1 Comment

There is a limit to the amount of power we can extract from the wind.

Imagine a circular column of moving air, or wind, 2 meters across. We can calculate how much power is in that moving column of wind with the following

Wind Power = Air Density / 2 * Area * Velocity³

Where Air Density = 1.225 kgm³ at sea level, and Area = Pi * R², in our case, 3.14m²

Say we wanted to calculate the power at a wind speed of 5ms ( 18kmh, an average windy day ), we use

1.225 / 2 * 3.14 * 5³ = 240watts

How does wind speed affect the power? A great deal! If we double our wind speed to 10ms ( 36kmh ), we end up with 1920watts! That is why its important to know how much wind speed you have, and why windmills are put on tall towers, to get as many extra ms as possible.

Getting back to our average windy day wind speed, the 240 watts is how much power is in that column of moving air, but its not how much we can extract from it to do work.

Air is a compressible fluid. If we face a 2 meter diameter disc into the wind, there will be some force against the disc from the wind, but not the full 240 watts worth. The wind will go around the disc, and most of the power goes with it.

What about a turbine? A turbine extracts much more energy from the column of moving air than the disc did, because the air is moving through the turbine, not around it. But some air will still go around. How much air goes around depends on many factors, like turbine design and loading.

There is a limit to how much energy we can extract from a column of moving air, called Betz.

http://en.wikipedia.org/wiki/Betz'_law

And Betz tells us we can extract no more than 59% of the energy of the moving column of air. There is a point where the air will just go around instead of through, adding extra widgets to the turbine, funnels, etc, wont help, the air will just find it easier to go around. The maximum efficiency of a turbine can not exceed 59%.

In reality, the true power we can extract is much less than the Betz limit. A multi blade farm windmill has a typical efficiency of 15%, and modern large scale wind turbines are closer to 40% efficient.

So adding to our formula

Shaft Power = Air Density / 2 * Area * Velocity³ * Turbine Efficiency

where Turbine Efficiency would typically =15% to 40%

So if we attach a shaft to our 2 meter wind turbine, we would expect to extract about 96 watts of shaft power from the 5ms wind.

Next we use our shaft power to drive a alternator/generator, and again, we will get out less than we put in. A good alternator is somewhere between 70% to 90% efficient, so for the sake of this example, we'll use a 80% efficient alternator. 96 watts shaft power will convert to about 77 watts of electrical power.

So our 2 meter turbine, in a 5ms wind, could be expected to make 77 watts of electrical power. Adding to our formula again we get

Electrical Power = Air Density / 2 * Area * Velocity³ * Turbine Efficiency * Alternator Efficiency

where Alternator ( or Generator ) Efficiency would typically = 70% to 90%

Turbine diameter and wind speed have a dramatic effect on the electrical power we get extract. If we increase the turbines diameter to 3 meters, we get a turbine area of 7 meters, more than double the original turbines area. Punch the figures in and we get 535watts wind power, 214watts shaft power, and 171watts electrical power.

What about wind speed? Back to our original 2 meter turbine, double the wind speed to 10ms, gives us 1923watts wind power, 769watts shaft power, and 615 watts electrical power.

That's why its important to have the biggest turbine you can manage, and the best wind. A 1.5 meter turbine mounted on the roof or in the back yard is going to make very little power compared to a 3 meter turbine on a 10 meter mast, its all in the maths.

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Importance of the Location for Small Wind Turbines

9:16 PM No Comments

Wind is the fuel that drives a wind turbine. A windmill needs to be placed where the wind is; putting it on too short a tower is like installing solar photo voltaic panels in the shade. Neither will work very well. Not just any wind will do, a wind turbine needs air that moves uniformly in the same direction. Eddies and swirls, ‘turbulence’ in short, do not make good fuel for a wind turbine. The rotor cannot extract energy from turbulent wind, and the constantly changing wind direction due to turbulence causes excessive wear and premature failure of your turbine. This means that you want to place your turbine high enough to catch strong winds, and above turbulent air. Since the tower price goes up quickly with height there is a limit to what is practical and affordable. This section is intended to help you decide what tower height works best.

The quick-and-dirty rule of thumb for turbine height is a minimum of 10 meters (30 feet) plus the length of a turbine blade above the tallest obstacle (trees, house etc.) in a 150 meter (500 feet) radius, with a tower height of at least 19 meters (60 feet). If the obstacle is more solid than a few trees (for example a whole tree line) then even more distance than 500' is needed, as will be described below.

This should really be regarded as an absolute minimum for a wind turbine; at 10 meters above an obstacle there will still be some amount of turbulence and additional clearance is highly desirable. Keep changes in height of obstacles in mind as well. For example, if you have trees that are expected to grow up to 60 feet high, it is advisable to use a 100 feet tower. Likewise, a 60 feet tower should only be used when the terrain is very, very flat with no obstacles in a wide area around, for example at the edge of the sea, or on top of a cliff with a clear area around it, or in the tundra. For most situations a 60 feet tower will only save a little money up front, while short selling energy production in the long run.

To go beyond the rule of thumb, the airflow over any blunt obstruction, including a tree, tends to create a “bubble” of turbulent air of twice the height of the obstacle, extending 20 times the height of the obstacle behind it. So, your 30 feet high house disturbs the air up to 600 feet away. That tree line with 100 feet trees disturbs the air up to 200 feet high at a distance of 1000 feet away! The figure above illustrates this. Locate your wind turbine either upwind of the obstructions, or far enough downwind. Notice from the figure that preference should be given to a site upwind of obstructions, but keep in mind that tall features downwind of the turbine can also influence the wind going through the blades, as shown in the figure.

Upwind and downwind are relative to the prevailing wind direction; where the wind blows from most of the time. A wind atlas can sometimes tell you what your prevailing wind direction is, and if there is one at all. Some sites have winds that did not read the rule book, and there it is equally likely to blow from more than one direction.

When it comes to wind turbines, the bottom of a hill, valley, or ravine makes for a poor place to site a windmill. The wind tends to drop in speed at the bottom of a smooth hill, then speed up as it goes up the hill, reaching around twice the wind speed at the top of the hill. The figure below shows this. You can use this effect to your advantage if you have hills on your property.

For obstructions that are not smooth, such as a cliff (i.e. a sudden rise in the landscape) it gets trickier: Sharp edges create turbulence, as illustrated in the figure below. The airflow at the top of the cliff can be stronger than the average wind speed in the area, but close to the cliff’s edge it may also be very turbulent, making it a poor site for a turbine. If you have a cliff edge on your property and want to use it for siting your turbine, you should still use a 60 feet high tower to get above turbulent air. Even if it seems that the wind is always blowing hard at the cliff’s edge.

The lee side (downwind of the prevailing winds) of a bluff object makes for a very poor wind turbine site. The bluff object will create large turbulence on its downwind side, and the average wind speed will drop off precipitously as well. This leaves no energy for the wind turbine to harvest.

There actually is a cheap way to visually find out at what height turbulent air ends, and smooth, laminar airflow begins. Just fly a kite at your proposed wind turbine location on a windy day, preferably when the wind is coming from the prevailing direction. To visualize airflow, use tape-streamers tied to the kite’s string every 15 feet or so (home improvement stores sell plastic marking tape in fluorescent colors for very little money). Wildly fluttering tape indicates turbulence, smoothly extended tape means smooth air. Be sure to take the angle of the kite’s string into account when calculating height.

The energy in the wind increases with the cube of the wind speed (P ~ v³), and wind speed increases with height. An increase of just 26% in wind speed means twice as much power available in the wind, and your wind turbine will produce almost twice as much. Double the wind speed and you an harvest almost eight times as much power! A small additional investment in tower height may therefore be well worth it, thanks to the increased energy production. If you know the annual average wind speed for your location (from weather data, a wind atlas, local weather station etc.) Weather data usually reports wind speeds at 10 meters above ground level, the spreadsheet can take care of translating that to a wind speed at turbine height. For a quick idea of how changes in tower height affect the power in the wind for an unobstructed site see the figure below.

The Danish Wind Power Association made a very nice, interactive, calculator that allows one to plug in various obstacles (for example, a row of trees), set their height and distance to the wind turbine, and visually show what effect this will have on wind speed and energy. The calculator shows the percentage of the wind speed at various distances and heights behind the obstacle. Keep in mind though that the effect of obstacles is not just to diminish wind speeds, but they also make the air swirl, creating turbulence. Turbulence is an energy thief when it comes to wind turbines.

If you have sufficient space for guy wires, we advise to use a tilt-up tower for your wind turbine. They are economical, costing only a little bit more than the cheapest type of tower (a fixed guyed tower), and allow the turbine to be installed on the ground. Maintenance can also be done on the ground, by tilting the tower down. This saves in crane expenses, and makes installation and maintenance much safer because the work does not have to be done at dangerous heights.

Another aspect of proper windmill siting is the distance from occupied buildings. All wind turbines produce some amount of sound. Even though the Scirocco is one of the most quiet wind turbines on the market (no, this is not just marketing hype, it really is quiet), it too produces sound. Some people find its sound soothing, since it tells them they are making energy, while it drives others absolutely bonkers. For that reason it is a good idea to place your wind turbine some distance away from your house, 100 feet is a good number for minimum separation. That is not to say that closer cannot be done, but you will have to honestly assess how the turbine’s sound will affect you. Generally, a Scirocco that is placed in smooth air will be almost inaudible unless the wind starts blowing hard. At that point the blades pitch to stall angle, causing the air to swirl across the blades instead of flowing smoothly, and this increases the audible sound. When this happens it can be heard over the wind when you are in close proximity (and downwind sound will carry further than upwind). There also is such a thing as too much distance, since the length and gauge of the wiring that is needed will increase. With the ever-increasing price of copper this makes it more expensive to install your turbine.

Since we are talking about buildings: Despite the current marketing pitch of many small wind turbine manufacturers and sales people, it is generally a very bad idea to mount a wind turbine (any turbine, not just a Scirocco) directly onto a building. The airflow that close to the building is generally very turbulent, leading to premature failure and poor power production. It is usually noisy too. Every wind turbine has some amount of vibration associated with it, and this too will be transmitted inside the house. We know, the thought of bolting a little turbine to the house, just over the roof line, to offset your electricity use (as that salesman put it) is appealing. The harsh reality is that it does not work: Several studies were done, involving dozens of roof-top-turbines. They all concluded that those turbines do not work. Their energy production is negligible, and some were even net-users of electricity (because their inverters draw power, even when nothing is going into the grid)!  Just say "no" to building mounted turbines!

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All About Small Wind Turbines

8:37 PM 2 Comments

How do residential wind turbines work?

A wind turbine, which is installed on top of a tall tower, collects kinetic energy from the wind and converts it to electricity that is compatible with a home's electrical system. In a residential application with net metering, a home is served simultaneously by the wind turbine and a local utility. If the wind speeds are below cut-in speed (usually a minimum of 2 or 3 meters per second is required) there will be no output from the turbine and all of the needed power is purchased from the utility. As wind speeds increase, turbine output increases and the amount of power purchased from the utility is proportionately decreased. When the turbine produces more power than the house needs, the extra electricity can be sold to the utility if such arrangements are available. All of this is done automatically.

Don't I have to take wind measurements for a year or more? 
For many residential systems the cost of taking wind measurements is not justified. Wind resource data provided by Environment EU is often sufficient for an experienced evaluated to predict wind turbine performance. For larger turbines and larger investments, it may be wise to collect more detailed data by location.

What about towers? 

A rule of thumb for proper and efficient operation of a wind turbine is that the tower height (turbine hub height) should be at least 10 meters above anything within 100 meters of the tower. Typically, 25 to 37 meter towers may be supplied along with the wind turbine, which usually avoids turbulence from buildings and trees on most sites. Wind speed increases the higher you go above ground, and it also becomes less turbulent. In addition, electricity generation from a turbine increases exponentially with wind speed. Thus, relatively small investments in increased tower height can yield very high rates of return in electricity generation. For instance, installing a 10 kW generator on a 30 meter tower rather than an 18 meter tower involves a 10% increase in overall system cost but can result in ~30% more power. Several different types of towers are available, depending upon which manufacturer you select. Each type has its advantages; the most economical tower is the ‘guyed lattice’ tower, but a hinged tower may be easier for you to install yourself and provides easier access for maintenance.

How reliable are wind turbines? Much maintenance?

Most small turbines have very few moving parts and do not require any regular maintenance. They are designed for a long life (up to 20 years) and operate completely automatically.

How would I have a wind turbine installed at my home? Most dealers offer either complete turnkey (ready-to-operate) installations or the option to purchase direct from the factory and install the system yourself. The first option offers more customer support from the company. Self-installation offers significant savings and a hands-on understanding of the turbine. Prospective owners can discuss the options available with manufacturers to decide which method best suits their budget and technical skills.

Approach buying the equipment as you would any major purchase. You may begin this process on our Help with Planning page. You will need to weigh costs and various degrees of rugged/durable designs. Obtain and review the product literature from several manufacturers, and research those you want to pursue to ensure they are recognized businesses and their parts and service will be available when you need them. Find out how long the warranty lasts and what it includes, and ask for references of customers with installations similar to the one you are considering. Ask system owners about performance, reliability, maintenance and repair requirements, and whether the system is meeting their expectations.

How many turbines to power a household or farm? 

For a home or farm, one turbine is normally installed. The turbine's size is chosen to meet the energy requirements given the available wind resource.

What about new small wind turbines that run at very low wind speeds?

Many companies have developed turbines that run at low wind speeds. But because the energy available in the wind is a function of the cube of the wind speed, there is very little energy available to be harvested at wind speeds less than 3 or 4 m/s (10 or 14 kilometers per hour). If you are considering the purchase of a small wind turbine for use in a low wind speed location, shop for turbines with good low wind speed performance; this may mean turbines with larger-than-average rotor diameters for their rated power.

Is a windmill or an electrical wind turbine better for pumping water? 

To pump water using wind energy, you need to place a windmill directly above your pumping site since windmills pump water through mechanical motion rather than using electricity. While this may be appropriate for some users, the wind speed at their desired pumping site may not be strong enough or may be obstructed by trees, embankments, etc. or the foundation at the pumping site may not be stable enough to install a windmill. Therefore, for some users, it may be more desirable to erect an electricity-generating wind turbine where the wind is favorable and run electrical cable to the pumping location, where you use an electrical water pump. Which is more practical and economically feasible for you depends on your property and wind regime.

Small Wind Economics

Will a small wind turbine save me money? 

Since energy conservation is usually less expensive than energy production, making your house or farm more energy-efficient first will likely reduce the amount of investment in a wind system to meet your needs. Most wind system purchasers have done all the reasonable efficiency measures first.

A wind turbine typically lowers a household electricity bill by 50% to 90%. It is not uncommon for wind turbine owners with total-electric homes to have monthly utility bills of only $8 US to $15 EU for nine months of the year in the EU. In northern parts of the EU. where less air conditioning is used the bills can be very low year-round. The amount of money a small wind turbine saves you in the long run will depend upon your electricity costs, the amount of electricity you use, the average wind speed at your site, and other factors.

How much does a wind system cost? 

It depends on the size of the turbine and electric demands. But you can also build your own homemade wind turbine easily... See: homemade 1 kW wind turbine

What should I watch out for in buying a small wind turbine? 

"If it seems too good to be true, it probably is" are words to keep in mind when shopping for a small wind turbine. Over the years, a steady stream of "breakthrough" wind turbines has promised exceptional performance at an incredibly low price. Sometimes the claimed performance violates the laws of physics, promising more power than the total kinetic energy available in the wind-stream that is intercepted by the rotor's swept area. Most of the popular models of small wind turbines operate at about the same efficiency. The energy production you should expect will be closely related to the swept area of the rotor blades, which is based on the diameter of the rotor. If you are offered a product that promises to run your whole house with a turbine that is much smaller than conventional products, it's time to start asking hard questions.

How do small turbine costs compare to other alternatives? 

Small wind turbines (ranging in size from 250 watts to 50 kW) are often the least expensive source of power for remote sites that are not connected to the utility system. Hybrid systems -- wind/photo-voltaic, wind/diesel, and other combinations -- can often provide the most efficient and cost-effective option for rural electrification. Photo-voltaic (PV) -- the direct conversion of sunlight into electricity -- is often used to supplement wind power since PV tends to operate best in low wind months. Diesel generators or batteries can be used for backup power and to maintain power production during low wind seasons.

One study of an Arctic community with annual average wind speeds of 15 mph (24 kilometers per hour) compared the cost of a 500-kW diesel system to that of a 200-kW diesel generator and four mid-sized wind turbines. It found that the wind/diesel combination cost considerably more to install ($378,000 EU versus $125,000 EU), but would deliver fuel savings of $90,000 EU per year, paying for itself in less than three years.

Small Wind and Your Environment

Do wind turbines make noise or interfere with TV reception? 

Small wind turbines do make some noise, but this is not a problem as long as the turbine is well-sited and located at least 200 meters from occupied buildings. Small wind turbines do not interfere with TV reception. See our Social, Environmental, and Other Considerations page for more details

Do small wind turbines kill birds? 

Anecdotal evidence indicates that birds occasionally collide with small wind turbines, as they do with any other type of structure. However, such events are rare and very unlikely to have any impact on bird populations. House cats in the EU, by contrast, are estimated to kill roughly one billion birds each year. Statistically, a single house cat is a much greater threat to birds than a small wind turbine. See our Social, Environmental, and Other Considerations page for more details

Are small wind turbines safe? 

·         Yes. However, neighbors who are uneasy about a nearby homeowner installing a small wind turbine may raise all sorts of questions about safety. Brief answers to some of these concerns:

• Falling tower: Thousands of wind turbines are installed in the EU, and their safety track record is excellent. Trees are much more likely to fall than a properly installed wind turbine, but no setbacks or minimum property sizes are required for trees.
• Safety of utility repair personnel during a power outage: Small wind systems shut down automatically in the event of a power outage, and will not energize a dead power line.
• Ice throw from rotor blades: Ice buildup makes wind turbine blades less aerodynamic, so that they turn more slowly. Typically, ice will drop to the base of the turbine tower instead of being thrown.
• Children climbing the tower and falling: Possible, but wind turbines should be treated no differently than other climbable structures such as water towers or amateur radio antennas.

Small Wind Grid Connection and Legal Issues

Will my utility allow me to hook up a wind generator? 

More and more provincial and regional utilities in EU have been developing and implementing interconnection and net metering policies to allow customers to buy/sell electricity to/from the national grid. Please contact your utility directly to find out their most recent news regarding interconnection and net metering.

Will I have to change any of the wiring in my house? 

No. A wind turbine can easily be installed at virtually any existing home without the need to change any wiring or appliances..

Will my local government allow me to install a wind turbine? 

A wind turbine is a tall structure that normally requires a building permit. Zoning regulations often limit the height, placement, and other characteristics of "appurtenant" structures, so a conditional (special) use permit or variance may be necessary. It's usually best to let your neighbors know about your installation. Be prepared to answer questions and clear up common misconceptions with well-documented facts about small wind turbines.

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Cost Saving with Small Wind Turbines

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Small wind turbines have a high potential to be part of a decentralized renewable energy system. Though costs are high and profitability is still low. For several years now the small wind industry has been expected to reach a tipping point with an increase in sales volume and a drop in production costs. This assumption is being analyzed in this paper and further saving potentials in small wind turbine production costs are outlined. Based on small wind market reports in several countries a global market analysis for small wind turbines in the range of 1 kW to 5 kW has been performed. From the findings a relevant set of manufacturers have been selected to study manufacturing methods and development trends.

The global market segment has a size of 22 000 small wind turbines annually with China, the United States and Great Britain as leading countries. The sales of market leaders can be estimated to be between 1000 and 2000 units a year. For the main components potential future cost savings are being discussed.

The tower is found to be the part with the major saving potentials. Measures to lower production and installation cost include centrifugal casted, segmented fiberglass towers and slip-joint techniques to connect the tower segments.

This article focuses on grid-tied systems with capacities from 1 kW up to 5 kW rated power and takes on the U.S. Small Wind Industry Road map's thesis that the industry “is close to the ‘tipping point’ where production volumes would skyrocket, causing production costs to plummet”. There is a lot of empirical evidence proving further high expectations on imminent production and sales increase such as a “huge potential” and an “age for the industry to boom and prosper“ or an potential annual energy yield of 1.5 TWh for Great-Britain. However, the expectations on plummeting production costs need to be backed by specific measures in design, manufacturing, logistics or installation cost.

Present prices for small wind turbines range from 2300 €/kW to 4600 €/kW compared to about 1000 €/kW in large wind . Amortization of investments without state subsidies is only viable in off-grid applications and on sites with high wind yields. The objective of this poster is to presents cost saving potentials of small wind turbines.

Blades: Savings of about 70% with change to large scale industrial processes such as matched metal molding, pultrusion or RTM-Molding, DLR has developed a filament winding process for small wind blades manufacturing at an industrial scale which has not been put into practice so far.

Generator: Production costs for permanent magnet generators are made up to 70% of material with rare earth elements prices being the main cost driver. Fixed cost degression is possible though it only has limited effect on the overall price.

Bearings: Early small wind turbines used bearings with additional bearing flanges in their machine housing. These flanges were casted and machined parts and drove costs up. Present bearing concepts have integrated the bearings into the housing and thereby cut costs by approximately two thirds.

Tower: The tower is the component with the main effect on the overall price of the small wind system. Manufacturing choices concern raw material, joining processes and surface protection. Furthermore the tower design and quality has effects on installation, logistic and life cycle cost.

Tower design using new structure materials is under development and has large potential to reduce cost. Significant cost savings can come from centrifugal casted, segmented fiberglass tower and slip-joining concepts for the tower segments.

Controller and inverter: Inverter technology is largely derived from photo-voltaic applications and costs are estimated at 0.50 €/W [9]. Therefore small wind inverter technology benefits from manufacturing and R&D investments that have been driven by the larger PV industry and will continue to do so.

Logistics: To facilitate shipment and work sharing in international value chains worldwide the length and width of a 20' sea freight container as an international standard should be met. 

The article that production costs may plummet has been partly proven right. The large cost potentials by industrial composites manufacturing processes for rotor blades have been realized by a few large small wind and component manufacturers in the 1-kW- to 5-kW segment with annual production volumes near 1000 units. Further cost savings have been realized by improved bearing concepts in turbine design and by benefiting from R&D efforts on inverter by the PV-industry.

After all annual sales volume is a limiting factor for smaller companies to invest in cost cutting technologies. Future potentials will come from innovations in tower design and manufacturing technology.

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